1. Field of the Invention
The invention relates to a rotationally symmetrical fastening element with an axially centralized rounded tip for a friction-welded joint with a flat component.
2. Description of Background Art
Such a fastening element is presented in FIG. 6d of EP 1 250 210 B1. The fastening element consists of a pin with conically tapered end, the tip of which is rounded. For friction-welding, the rounded tip is pressed onto a flat component until, because of the arising heat of friction, the material of the pin and, where applicable, also of the component melts, whereupon, the retaining of the pin and the ensuing cooling of the friction-welding site results in the welded joint with subsequent solidification. The material that melts from the rounded tip is collected by a cup-shaped recess in the flat component, into which recess the tip is rotatingly pressed with strong pressure against the component in order to achieve the friction-welded joint.
A further embodiment of a fastening element used for friction-welding is disclosed in FIGS. 1 and 2 of U.S. Pat. No. 6,227,433 B1, which relate to an especially obtuse-angled tip, which, for the friction-welding operation, is lowered into a flat component, possibly piercing said component and penetrating into a further component, this resulting in a joint between both components, there being no particular place provided to receive the material that melts from the fastening element.
Furthermore, reference may additionally be made to DE 196 20 814 A1, in which a fastening element similar to the fastening element in the aforementioned U.S. Pat. No. 6,227,433 and having an especially obtuse cone angle is brought into engagement with a flat component. Through friction-welding as a consequence of rotation of the fastening element, the latter finally pierces a flat component and thereby comes into contact with a below-lying flat component, this resulting in the welding together of both components in the manner similarly disclosed in the aforementioned U.S. Pat. No. 6,227,433. Also in the subject matter of DE 196 20 814 A1, no special space is provided to receive the melted material.